chore(plugins): add [integrity] SHA-256 hashes for all hook scripts

The daemon's `manifest_missing_integrity_hooks` check (#3804) hard-fails
any registry install whose plugin.toml declares hooks but lacks an
[integrity] entry for each one. All 11 plugins under plugins/ had the
[hooks] table but were missing [integrity], so `librefang plugin install
<name>` would error after download with "missing [integrity] hashes for
hook script(s): ...".

Compute and pin SHA-256 over each `hooks/*.py` under every plugin dir.
The mempalace-indexer entries were already present and are unchanged
(reordered alphabetically by the regenerator).

Verified each plugin.toml still parses (Python tomllib).

plugins/context-decay/plugin.toml

@@ -35,3 +35,7 @@ description = "Decaimiento de memoria basado en el tiempo con puntuación de rel
 [i18n.fr]
 name = "Déclin du contexte"
 description = "Déclin de mémoire basé sur le temps avec scoring de pertinence pour un oubli naturel."
+
+[integrity]
+"hooks/after_turn.py" = "eb7801807e444bd9b804ee6c3b8b6cc68e29f08c3368f3d92e8047654eb0665b"
+"hooks/ingest.py" = "f9a82df0a460720d9888f179c31e8be0afd9b4dbc90329988e5347f9b7acf941"